Process for the separation of one or more constituents of liquid mixtures



Dec. 7 1926.

W. BADER PRoCEss FOR THE SEPARATION CE ONE OR'MORE CONSTITUENTS oF LIQUfD MIXTURE 9ct uiuc( WSOUSGQ mOleS Q51 urrmu( 1.22. ZmQJ QAII 2.2.5400 QM. J

- File uly e, 192:',

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INvErrroR WALTER BADER, By his Attorneys,

20 the water.

Patented ec.. 7, 1926.u

WALTER BADER, E 'sPo'NDoN NEAR DERBY, ENGLAND, AssIGNoR To AMERIc cELLULosE AND cIIEMIcAL MANUFACTURING COMPANY LIMITED, A 'coRroRA- TION OF DELAWARE. Y

ERocEss EoR THE SEPARATION 0E oNE v0R MORE .coNsTztTUENTs` 0E LIQUID MIxTUREs. p v

Application med July e, 1923, serial No. ciaaeaanaji Great Britain september e, 192e.

The usual way of separating the constituents of liquid mixtures is by fractional dis'- tillation, making use of the different boiling points ofthe constituents, or by extraction,

making use of their. different solubility in av solvent. In many cases, the application-of either method is technically or economically columnof reasonable dimensions and anv economical' expense v'of heat will not prevent a large amnt of acid distilling away with The present invention .deals with cases of this kind. It is based upon the following principle. f v

If the surface of'a liquid mixture containedfin a closed"vessel be covered by a thin layer'ofV an insoluble liquid oflower density but preferably muchhigher boiling` point (hereafter called the oil film), and if the whole arrangement be kept at some temperature below the boiling point of the v mixture, the vapour phase above the liquid will, after a certain time, have practically the same composition it would have if the oil film were not present, whatever the differencesin the' solubilities of the constituents in the 'oil film may be. The vapour of the oil film comes in simply as an addi-A tion. Since .absolute insolubility of two vliquids in f one another does not exist,- 'the' 40 different constituents of the mixture must, however little, dissolve in the oil film and exercise at the. surface of it their vapourtension, only slightly'modified by the small solvent power .of the o il.

If' the-vapour above the liquid be7 now continuously removed, for instance byblowf Ving an air current over the surface, thecom position of the vapour must change if the constituents of the mixture are differentlyv Soluble in the oii'alm. Each' Single coni stituent tends to replace its vapour carried The mutual solubility. of solvent and solute should be very small; a fractionv of 3%. gives -a sufficient technical eect.

. The new process may be carried out in any kind of apparatus in which-.the liquid mixture can be spread out .so as to present 70 a large horizontal surface. This surface is covered with a layer, preferably as thin as possible, of a liquid Vwhich, to be' suitable, should have the followingl properties (a) Very low solubilityin the mixture and, if possible, also in the distillate.

(b) Preferential solvent power for the vconstituent of the mixture which it is in-l tended to isolate.

' (c) Relatively .high boiling point;

(d) Lower density .than the mixture. (e) Capability to spread 4out easily upon the mixture to a thin, unbroken lm.

This liquid may, of course, be 'tselt a mixture. 8.5

The mixture is heated without raising tp boiling but preferably as high as it is pos; sible without bringing it to boil, and air or A any other .suitable gas or gas mixture, or` an' indifferent vapour, is blownf or drawn 90 over the surface of the liquid. After leaving the apparatus the gas or .indifferent vapour is led intoa cooling or absorbing sys'- tem where the vapours taken uprby it are blower or be returned to the apparatus,

vwhereby a closed system, may established so 'i tion, the section being without any loss of uncondensed vapours.' The evaporating system may be worked at any convenient pressure.` The'air or gas may be compressed or even liquied for the recovery of the vapour. The heating of the liquid may be done in any convenient way, in particular by means of the working gas itself, which can be heated before admissionV taining the trays and air heaters.

Example,

Dilute acetic acid, for instance ofv30-% strength, is contained in wide, Hat trays 1 vof acid resisting material, the acid being admitted, preferably hot, to the uppermost tray by the inlet pi e 2, and overflowing from tray to tray. e surface of the acid in the tra s is covered vwith a thin layer ment all the trays are fed from above,

of a high oiling petroleum distillate, indicated by the broken line l3, e. g. a spindle oil which will dissolve about 0.3% of its weight of acetic acid, but will only dissolve the merestvtrace .of water. A number of the trays 1 are arranged one above the other 1n a` closed heat insulated chamber 4, so

that a narrow free space' remains between.

thel liquid in one trayiand the bottom of the next tray. .Each tray 'has an overflow 5, takmg the liquid from its bottom into' the tray below, by means of which arrangeresidual acid leaving the bottom of the chamber at 6.

-Air is supplied by a` blower -7 preferably via a. heat interchanger 8, to the lowest tray between each two trays, the airA current is 1ed',-fpreferably via the hea-tv interchanger 8,

after having passed a heating system, e. g". a radiator-heater R which brings. its temperature to about 100 C., the air passing over the outside of the heating 'pipes 9'of the radiator which are provided withy ribs or gllls 9 in the usual way. The air-passes over the/surface of the liquid in the lowest tray 1,. then overa second heater, marked R1, slmllar to the first, to regain the re quired temperature vof ,about 100 C., iiows over the second tray, and so on over the successive trays and similar heaters marked R2, RSR, R5, interposed respectively between each two trays. After thus passing over allthe trays in series, with'heating up` may pass through freezing mixture. Practically all the acetic toa condenser 10, in which for example it i a copper coil cooled by a acid vapour is condensed in the condenser and can be collected in a receiver 11. The air from the receiver. is conducted back to thev blower-7 by the pipe 12 so that any vapours it mayy still contain -are returned to the chamber containing the trays. 'Preferably the outgoing air from the series of trays is used to preheat' the ingoing air 1n a heat interchanger as illustrated for example in the figure in which the air from the blower 7 is delivered by the ipe n13 through the heat exchanger 8, to t e pipe 14 leading to the heater R of the bottom tray, and the vapour-laden air current from the top tray passes by the outlet pipe 15 to the heat interchanger and from the latter to the condenser by the connection 16. The heat interchanger may of course be of the usual construction in which the current in one direction passes through tubes and that in the opposite direction over the outside 'of the tubes. t

With a working such as described it has 1 been found, for example, that 1000 sq. ft. l

of liquid surface can yield about 1 Iton of distillate in 24 hours. This distillate contains about 60% acetic acid, a small amount of oil floatingon it. If a higher concentration is desired, the distillate may again be treated in the same way, which brings it to over 80% strength. A third treatment f can yield an acid of 92% to 95% Strength. replaced 'from time to time in the trays aS required. V v

What 'I claim and desire to secure Iby Letters yPatent is e 1. A process for the separation of one or Oil which distils away may be` L more constituents out of a liquid mixture, I

`current from which they are subsequently.

recovered.- e e 2. In a process according t0 claim -1, returning the gas or vapor from which thel vconstituents have "been recovered so that a closed circuit 1s formed.

- 3. In a process according to clailn 1, heat-Y ing the as or vapour before .admlsslon to theliquld surface, thus using the' as or vapour as a heating medium for the 'quid ly 4. The process of claim 1 in which thef liquid. mixture is aqueous acetic acid.

5. In a process according to claim 4, the fuse of petroleum distillates as-solvents.

6. process for the concentration of ace- 1,609,393 y v l y of, comprising covering the surface of the tion to a point somewhat below boiling, and

[dilute acetic acid solutlon witha film of a recovering from the. air current'the acetic 10 high boiling solvent having a selective solacid vapors taken up thereby.

5` vent power for acetic acid, circulating over/ In testimony lWhereo I have hereunto the {ihn-covered acetic acid solution a rapid subscribed my name.' f current of heated air maintained at a tem- 'l WALTER BADER.

tic acid from dilute aqueous solutions thereperature adapted to heat the acetic acid solu- 

